Mount arrangement for torque roll vibration isolation

Abstract

A mounting arrangement for mounting a rotary engine to an aircraft structure, wherein the engine has a three orthogonal axes comprising: a roll axis; a pitch axis; and a yaw axis. The mounting arrangement comprises: one-degree-of-freedom links with reaction axes passing through the roll axis. A separate roll constraint has a moment reaction about the roll axis to decouple the torque roll mode from the other one-degree-of-freedom links.

What is claimed is: 
     
       1. An aircraft engine assembly comprising:
 a rotary engine having a roll axis, a pitch axis and a yaw axis extending through a center of gravity of the rotary engine, 
 a first set of one-degree-of-freedom links mounted to a first side and a second side of the rotary engine, the first set of one-degree-of-freedom links having a distal end configured to be mounted to an aircraft and a proximal end mounted to the rotary engine, the first set of one-degree-of-freedom links positioned relative to the rotary engine to have respective reaction axes passing through the roll axis; and 
 a second set of links having a distal end configured to be mounted to the aircraft and a proximal end mounted to the rotary engine, the second set of links positioned relative to the rotary engine to have respective reaction axes transversally spaced-apart from the roll axis wherein the first set of one-degree-of-freedom links has a first mounting stiffness, and the second set of links has a second mounting stiffness, wherein the second mounting stiffness is less than the first mounting stiffness. 
 
     
     
       2. The aircraft engine assembly according to  claim 1 , wherein the first set of one-degree-of-freedom links include a pair of forward links and a pair of rearward link and an axial constraint link having a reaction axis parallel to the roll axis; the forward links, the rearward links and the axial constraint link having a first mounting stiffness, the second set of links having a second mounting stiffness, wherein the second mounting stiffness is less than the first mounting stiffness. 
     
     
       3. The aircraft engine assembly according to  claim 1  wherein the second set of links comprises: a pair of one-degree-of-freedom roll links, the roll links having reaction axes non-parallel to the roll axis and spaced a transverse distance X from the roll axis. 
     
     
       4. The aircraft engine assembly according to  claim 3  wherein the pair of one-degree-of-freedom roll links is an opposing pair of said one-degree-of-freedom roll links disposed on opposing sides of the roll axis. 
     
     
       5. The aircraft engine assembly according to  claim 2  wherein the second set of links comprises:
 a pair of A-frames each having two non-parallel one-degree-of-freedom links, each non-parallel one-degree-of-freedom link having a distal end configured to be mounted to the aircraft spaced apart an axial distance and a proximal end mounted to the rotary engine. 
 
     
     
       6. The aircraft engine assembly according to  claim 5  wherein the proximal ends of the non-parallel one-degree-of-freedom links of the A-frame are joined at a trunnion. 
     
     
       7. The aircraft engine assembly according to  claim 6  wherein the trunnion includes an axial segment defining the axial constraint having the first mounting stiffness and a radial segment defining the roll constraint having the second mounting stiffness. 
     
     
       8. The aircraft engine assembly according to  claim 7  wherein the pair of A-frames is an opposing pair of said A-frames disposed on opposing sides of the roll axis. 
     
     
       9. A method of mounting a rotary engine to an aircraft structure, wherein the engine has a three orthogonal axes comprising: a roll axis; a pitch axis; and a yaw axis extending through a center of gravity of the rotary engine, the method comprising:
 mounting a forward portion of the engine to the aircraft structure with an opposing pair of non-parallel one-degree-of-freedom forward links having a reaction axis passing through the roll axis; 
 mounting a rearward portion of the engine to the aircraft structure with an opposing pair of non-parallel one-degree-of-freedom rearward links having a reaction axis passing through the roll axis; 
 axially constraining the engine with an axial constraint having a reaction axis parallel to the roll axis; and 
 rotationally constraining the engine with a roll constraint having a moment reaction about the roll axis; 
 wherein the forward links, rearward links and axial constraint have a first mounting stiffness, and the roll constraint has a second mounting stiffness, wherein the second mounting stiffness is less than the first mounting stiffness. 
 
     
     
       10. The method according to  claim 9  wherein the engine is rotationally constrained about the roll axis using a one-degree-of-freedom roll link having a reaction axis non-parallel to the roll axis and spaced a transverse distance from the roll axis. 
     
     
       11. The method according to  claim 10  wherein the engine is rotationally constrained about the roll axis and axially constrained parallel to the roll axis using a pair of opposing A-frames disposed on opposing sides of the roll axis. 
     
     
       12. The method according to  claim 11 , wherein the A-frames have two said one-degree-of-freedom roll links joined at a transverse trunnion. 
     
     
       13. The method according to  claim 12 , wherein the trunnion includes an axial segment defining the axial constraint having the first mounting stiffness and a radial segment defining the roll constraint having the second mounting stiffness. 
     
     
       14. An aircraft mount for a rotary engine comprising:
 an opposing pair of non-parallel one-degree-of-freedom forward links attached to a forward portion of the rotary engine and an opposing pair of non-parallel one-degree-of-freedom rearward links attached to a rearward portion of the rotary engine, the forward and rearward links having respective reaction axes passing through a torque roll axis of the rotary engine; and 
 an A-frame link on each side of the engine between the forward and rearward links, the A-frame link oriented with a reaction axis transversely spaced apart from the torque roll axis, the reaction axis of the A-frame link being non-parallel to the torque roll axis and configured to restrain axial and roll movement; 
 wherein the roll movement is restrained with a roll constraint of roll stiffness lower than an axial stiffness of an axial constraint and lower than a link stiffness of the non-parallel one-degree-of-freedom forward and rearward links. 
 
     
     
       15. The aircraft mount according to  claim 14  wherein the A-frame link includes a trunnion mounted to the engine. 
     
     
       16. The aircraft mount according to  claim 15  wherein the trunnion includes an axial segment defining the axial constraint having the axial stiffness and a radial segment defining the roll constraint having the roll stiffness.